Method for automatically washing the inking circuit in rotary printing presses and plant for implementing said method

ABSTRACT

The invention relates to a plant for automatically washing the inking circuit in rotary printing presses, comprising a chamber ( 2 ) for inking cylinder ( 1 ); lines ( 4′, 4, 6, 8, 8′, 8 ″) which connect said chamber ( 2 ) to a tank ( 3 ) for the ink; means ( 5 ) for pumping the ink from said tank ( 3 ) via said lines ( 4′ 4, 6, 8′, 8 ″) to a said chamber ( 2 ) and from the latter to the tank ( 3 ) again; a tank ( 23 ) for the clean solvent; lines ( 22, 20 ′) provided with means able to connect said tank ( 23 ) to said line ( 4 ); a tank for the dirty solvent ( 12 ′) and lines ( 15, 12 ) provided with means able to connect said tank ( 12 ) to said line ( 8 ′). According to a main characteristic feature of said plant, the means ( 5 ) for pumping the ink consist of a peristaltic pump, the rotor of which is actuated by a motor with a reversible direction of rotation. The invention also comprises a method for automatically washing the inking in rotary printing presses using the abovementioned plant, which method is characterized by the step of intermittently introducing air into the flow of solvent circulated in the lines to be washed, which produces an intermittent acceleration of the body of solvent inside the lines, increasing the action of separation of the ink from the walls of the lines by the solvent.

The present invention relates to rotary printing presses such as, forexample, flexographic printing presses or offset printing presses, andmore particularly relates to a method for automatically washing theinking assembly of the printing cylinders in these presses and the partsassociated with the circuit thereof, in particular, although notexclusively in presses of the abovementioned type for polychromaticprinting.

The present invention relates furthermore to a plant for implementingthis method.

EP-0,780,228 discloses a method and a device for cleaning the doctordevice of an inking assembly of a rotary printing press. In accordancewith this method, the ink is returned from the inking compartment to theink tank again. Subsequently, solvent is pumped into the inkingcompartment and is then conveyed into the ink tank via the ink supplyand discharge lines. Thereafter, the solvent contaminated by the ink ispumped into the dirty-solvent tank, clean solvent being then pumped in aclosed circuit along the ink supply and discharge lines for a certainperiod of time and then discharged into the dirty-solvent tank. Theplant for implementing this method requires a plurality of pumps forsupplying and discharging the ink from the inking chamber, which, inaddition to a constructional complication, also has the drawback thatthere are zones of the line which are never cleaned in a satisfactorymanner.

Moreover, the solvent used in the washing operation is not recycled—evenpartly—for the subsequent washing cycles, therefore negatively affectingthe costs of the process.

The object of the present invention, therefore, is to overcome thedisadvantages of the known methods for washing the lines for supplyingand discharging the ink from the inking chamber of a rotary printingpress. According to a main characteristic feature of the presentinvention, this object is achieved by using in the ink circuit a pump,the direction of delivery of which may be reversed by means of simplereversal of the direction of rotation of the pump's rotor. This objectis achieved advantageously, although not necessarily, using aperistaltic pump.

According to a further characteristic feature of the present invention,it has been found that it is possible to increase the action of thesolvent in the lines to be washed, by injecting intermittently air intothe flow of solvent, so as to make the body of solvent in the pipeselastically compressible, owing to the presence therein of the aircushions, so that the intermittent acceleration of the body caused bythe intermittent introduction of air therein also results in amechanical action of separation of the ink from the walls of the lines,which, added to the action of the solvent, allows particularly efficientcleaning of these lines.

According to a further characteristic feature of the present invention,the semi-dirty washing solvent is stored and used in the subsequentwashing cycle.

Advantageously, the whole washing process is automated, and this processrequires only very limited manual intervention for implementationthereof, which, if necessary, could also be automated.

Further objects and advantages of the automatic washing method accordingto the present invention will emerge more clearly during the course ofthe following description of a plant for implementing said method, shownschematically in the accompanying drawings, illustrating by way of anon-limiting example an embodiment of the washing plant according to thepresent invention, for washing the inking cylinder and the circuit,associated therewith, of a rotary printing press. In the drawings:

FIG. 1 illustrates schematically the inking circuit of the inkingcylinder of a rotary printing press during the step for supplying theink to the inking cylinder, with the washing circuit of the inkingcircuit in the inactive condition;

FIG. 2 is a view similar to that of FIG. 1, illustrating the step foremptying the ink from the inking lines and from the inking cylinder,with discharging of the ink into the ink tank;

FIG. 3 illustrates the first step for washing the inking circuit usingsemi-dirty recycled solvent and with discharging of the dirty solvent inthe tank for collecting this solvent;

FIG. 3A shows a longitudinal section through a detail of a part of asolvent conveying line containing portions of solvent separated by aseries of air bubbles;

FIG. 4 illustrates the second step for washing, in a closed circuit, theinking circuit using semi-dirty recycled solvent;

FIG. 5 illustrates the step for washing the inking circuit using cleansolvent, with collection of this solvent in the semi-dirty solvent tank;

FIG. 6 illustrates the final step of emptying from the inking lines thesolvent still contained therein using a high-pressure air flow whichprecedes the new inking step with supplying of new ink to the press; and

FIG. 7 shows a detail of a variation of embodiment of the circuit forwashing the inking chamber housing the doctor blades.

With reference to the drawings and with particular reference to FIG. 1thereof, 1 denotes the inking cylinder and for example the screenedcylinder (anilox cylinder) of a flexographic printing press. 2 denotesthe chamber for supplying the ink to the cylinder 1, which also containsa scraper or doctor blade (not shown) having the purpose of ensuring auniform layer of the ink film on the surface of the cylinder 1. 3denotes the ink collection tray into which the line 4′, connected bymeans of the quick-action coupling 10 and the line 4 to the pump 5,leads. According to a characteristic feature of the present invention,the pump 5 is of the type having a reversible delivery and intake, andin particular said pump is a peristaltic pump. The pump 5 is connectedin turn by means of the line 6 and the pneumatically controlleddiaphragm valve 7 to the chamber 2. The chamber 2 is in turn connectedby means of the line 8, the diaphragm valve 9, the line 8′, thequick-action coupling 11 and the line 8″ to the tank 3. Therefore,during the course of a normal printing operation, the ink I contained inthe tank 3 is circulated by the pump 5, being sucked via the line 4′,the coupling 10, the line 4, the line 6 and the valve 7 into the chamber2, where it is spread onto the inking cylinder 3, and is made to flowfrom the chamber 2 via the line 8, the valve 9, the line 8′, thequick-action coupling 11 and the line 8″ back into the tank 3 from wherethe ink is again supplied to the cylinder 3, thus closing a continuouscycle for supplying ink to the inking cylinder 1.

The plant is completed by a line 12 provided at one end with aquick-action coupling element 11′ and connected to the double-diaphragmpneumatic pump 13 connected to the twin valve 14 which in a firstposition discharges, by means of the line 15, into the tank 12′ for thedirty solvent Sp and in a second position discharges, by means of theline 16, into the tank 17 for the semi-dirty solvent SSp. The tank 17 isin turn connected, by means of a line 18 comprising a twin valve 19which, in one of its switched positions, connects the line 18 to theline 20 terminating in the quick-action coupling element 10′, while, inthe other switched position of the valve 19, the line 20 is connected tothe delivery of the pump 21, the intake side of which is connected tothe line 22 which leads into the tank 23 containing the clean solvent S.The automatic washing circuit described is completed by a compressed-airsource 24 comprising a branch supplying air at a low pressure, forexample at a pressure of about 0.5 bar, connected by means of theshut-off valve 25 and the line 26 to the line 6 at a point between thepump 5 and the valve 7 and a branch supplying air at medium pressure,for example at a pressure of about 2 bar connected, by means of theshut-off valve 27 and the line 28 to the line 4 at a point thereofbetween the pump 5 and the quick-action coupling 10 and connected bymeans of the branch 29 to the line 8 at a point thereof between thequick-action coupling 11 and the shut-off valve 9, for the purposeswhich will be described below.

With reference to FIG. 2, the first step of the method for washing theinking circuit described above will now be described. During this step,the direction of pumping of the pump 5 is reversed, thus sucking all theink present inside the doctor-blade chamber 2 and in the line 6 andconveying it via the line 4 into the tank 3. At the same time, thebranch of the line 8 is also emptied by means of gravity into the tank 3so that the circuit formed by the lines 4, pump 5, line 6, chamber 2 andline 8 are at the end of this operation emptied of the ink therein whichis conveyed back into the tank 3 for the ink I. At this point one passesto the next step of the automatic washing step. This step, which isshown in FIG. 3, comprises preliminarily disconnection of thequick-action coupling elements 10 and 11 from the pipe sections 4′ and8″, respectively, and their connection to the quick-action couplingelements 10′ and 11′, respectively. This operation of disconnection andsubsequent connection of the quick-action couplings is preferablyperformed manually. However, this operation could also be automated bymeans of suitable robotized devices. Moreover, the valve element 19 isswitched so as to establish a connection between the line 18 and theline 20; the valve element 14 is switched so as to establish aconnection between the delivery of the pump 13 and the line 15 whichdischarges into the tank 12′ and the valve element 25 is intermittentlyswitched so as to establish communication between the source oflow-pressure air supplied from 24 and the line 26. During this step, theaction of the pump 5 is again reversed, so that operation of the pump 5causes suction of the semi-dirty solvent SSp from the tank 17, via theline 18, the valve 19, the line 20, the coupling 10′, 10, the line 4,the pump 5, the line 6 and the valve 7 into the chamber 2. As it passesalong the line 6, air at low pressure is injected at intervals from theline 26 into the line 6. This injection results in the formation, alongthe lines in question—and in particular the lines 6, 8 and 8′—as well asinside the chamber 2, of a series of air bubbles A which are arranged atmore or less regular distances within the flow F of solvent as shownschematically in FIG. 3A. The presence of these air bubbles, namely of afluid which can be compressed within the body of liquid, and the pulsesdue to the intermittent introduction of the air into the flow ofsolvent, produces a continuous intermittent acceleration of the body ofsolvent supplied through the chamber 2 and the lines 8 and 8′, and thisintermittent accelerating movement of the body of solvent results, withits mechanical action, in an increase in the removal of the inkperformed by the solvent from the walls of the pipes in question and thecomponents of the chamber 2. The solvent charged with ink resulting fromthis first operation is discharged from the line 8′ via the couplings11,11′, the line 12, the pump 13, the valve 14 and the line 15 into thetank 12′ for the dirty solvent Sp. During this washing step, the inkingcylinder 1 is run at a low speed.

During the following step, illustrated in FIG. 4, the valve 14 isswitched so as to connect the delivery of the pump 13 to the line 16.All the other connections remain, during this step, unchanged. At thispoint, the semi-dirty solvent from the tank 17 is circulated asdescribed with reference to the step in FIG. 3, with the sole differencethat, instead of being discharged into the tank 12′, it is recycledalong the line 16 back into the tank 17. During this step also, thepulsed injection of air into the flow of solvent continues via the line26. Below, in a manner entirely similar to that described with referenceto the first step of the cycle, emptying of the semi-dirty solvent fromthe lines is performed by means of reversal of the peristaltic pump 5.The semi-dirty solvent is therefore conveyed back into the tank 17. Atthe end of this new operating cycle, the valve 19 (see diagram in FIG.5) is switched so as to interrupt the connection between the tank 17 andthe line 20, and the latter is connected to the delivery of the pump 21associated with the tank 23 for the clean solvent. During this stepalso, the pulsed injection of air into the flow of clean solvent iscontinued via the line 26, and the solvent circulated in this way, asdescribed with reference to the step illustrated in FIG. 4, is collectedinside the tank 17 for the semi-dirty solvent.

At this point the final step of the automatic washing operationcommences. During this step the direction of the pump 5 is reversedfirstly so as to empty the pipes and the chamber 2 of the clean solvent,which is collected inside the tank 17. At the same time the flow oflow-pressure air from the line 26 is interrupted by means of switchingof the valve 25, and the valve 19 is reset to the switched positionshown in FIG. 4. Then the valves 7 and 9 in turn are switched into theclosed position so as to prevent the air at a pressure of 2 bar frompressurising the chamber 2. Finally, the valve 27 is switched so as toconvey a flow of air at a high pressure along the pipes, so as todischarge completely the solvent contained in them, performing alsodrying of the residual solvent in the said pipes. After this, it ispossible to perform disconnection of the quick-action couplings 10 and11 from the couplings 10′ and 11′ and reconnection thereof to the pipes8″ and 4′, re-establishing at the same time the operating conditionsdescribed with reference to FIG. 1.

Obviously the washing method according to the present invention is notlimited to the operating steps described and illustrated. Thus, forexample, it is possible to envisage using simplified and shortenedprocedures in the case where the press must be stopped for a relativelyshort period of time, without it being necessary to change the ink, inwhich case it is possible, for example, to omit the initial washingsteps using semi-dirty solvent.

FIG. 7 illustrates a variant of the cycle for washing the inking chamber2 of the printing cylinder 1. According to this variant, the lines 6′and 8′ are connected together by means of a line 9″, with insertion of avalve 9′ and, likewise, the lines 6 and 8 have been connected togetherby means of a line 7″ with the insertion of a valve 7′. Owing to thisparticular circuit arrangement it is possible to pump solvent which isboth clean and semi-dirty from those holes which under normal conditionsare the discharge holes of the chamber 2 and discharge solvent from thehole which under normal conditions is the hole supplying the doctorblade. In fact, by closing the valves 7 and 9 and opening the valves 7′and 8′, the result is obtained whereby the pipe section 8 is completelywashed, first with semi-dirty solvent and then with clean solvent.

Although reference has always been made during the course of thedescription to the pump 5 as being a peristaltic pump, it is understoodthat, instead of this pump, it would be possible to use twodouble-diaphragm pneumatic pumps, with two supply lines.

Obviously, in a polychromatic printing press, there will be as manymodules such as those described above as there are different printingstations.

The washing system according to the invention may be completelyautomated and its electronics may be incorporated into the electronicsof the printing press. It may be controlled by means of software whichallows the washing cycles to be programmed according to the specificrequirements of the individual users.

Obviously, the present invention is not limited to that described andillustrated, but comprises all those variants and modifications whichfall within the more general scope of the inventive idea, substantiallyas claimed below.

1. Plant for automatically washing the inking circuit in rotary printingpresses, comprising: a chamber for inking the inking cylinder; lineswhich connect said chamber to a tank for the ink; means for pumping theink from said tank along said lines to said chamber and from the latterback into the tank; a tank for the clean solvent; lines provided withmeans able to connect said tank to said line; a tank for the dirtysolvent and lines provided with means able to connect said tank to saidline, characterized in that said means for pumping the ink consist of aperistaltic pump, the rotor of which is actuated by a motor with areversible direction of rotation.
 2. Plant according to claim 1, inwhich said means able to connect said tank to said line and said tank tosaid line consist of quick-action couplings.
 3. Plant according to claim1, further comprising a tank for the semi-dirty solvent, switching valvemeans able to connect said tank to the lines and, respectively, via thelines and being provided.
 4. Plant according to claim 1, furthercomprising a source of compressed low-pressure air connected, by meansof shut-off means to a line which is branched to the line upstream ofthe inking chambers.
 5. Plant according to claim 1, further comprising asource of compressed high-pressure air connected, by means of shut-offmeans, to a first line which is branched to the line upstream of thepump and to a second line which is branched to the line 8′ downstream ofthe inking chamber.
 6. Plant according to claim 1, in which a pump isinserted into the circuit between said line and said switching valvemeans.
 7. Plant according to claim 1, in which a pump is inserted intothe circuit between said line and said switching valve means.
 8. Plantaccording claim 6, in which said pumps are pneumatic pumps of the doublediaphragm type.
 9. Plant according to claim 3, in which said source oflow-pressure air is a source of air at a pressure of between 0.3 and 0.7bar and preferably at a pressure of 0.5 bar.
 10. Plant according toclaim 4, in which said source of high-pressure air is a source of air ata pressure of between 1.5 and 3 bar and preferably at a pressure of 2bar.
 11. Plant according to claim 3, in which means are provided forsupplying said low-pressure air in the line by means of closely spacedintermittent pulses.
 12. Plant according to the claim 1 in which,adjacent to the chamber, the lines and are connected together by meansof a line, with the insertion of a valve, and likewise the lines and areconnected together by means of a line with the insertion of a valve soas to allow both clean and semi-dirty solvent to be pumped from what isunder normal conditions the discharge hole of the chamber and allowsolvent to be discharged from the hole which under normal conditions isthe hole supplying the said chambers, so that, by means of closing ofthe valves and opening of the valves and, it is possible to washthoroughly, first with semi-dirty solvent and then with clean solvent,the pipe section.
 13. Method for automatically washing the circuit inrotary printing presses using the plant in accordance with claim 1,comprising the steps of: inverting the direction of rotation of therotor of the pump so as to empty the ink contained in the chamber and inthe lines, conveying it back into the tank and at the same time causingthe ink contained in the lines to flow back by means of gravity into thesame tank. disconnecting the quick-action coupling elements from thelines and connecting them to the quick-action coupling elements;switching the valve element so as to establish communication between theline supplying the semi-dirty solvent from the tank and the linecommunicating via the couplings with the line 4; switching the valveelement so as to connect the line, the couplings, the line and the pumpto the line leading into the tank for collecting the dirty solvent;renewed reversal of the direction of rotation of the rotor of the pumpso as to pump the solvent from the tank for the semi-dirty solvent viathe line, the chamber, the lines into the tank, with simultaneousopening of the valve so as to inject intermittently compressedlow-pressure air into the line, within the flow of semi-dirty solvent;switching the valve so as to connect the delivery of the pump to theline leading into the tank and continued circulation, in a closed cycle,of the semi-dirty solvent through the circuit of the chamber, continuingthe intermittent introduction of low-pressure air into the solvent whichis circulated; emptying from the lines the semi-dirty solvent by meansof reversal of the peristaltic pump, with conveying of the semi-dirtysolvent back into the tank; switching the valve so as to connect thetank for the clean solvent to the flow circuit of the chamber, withdischarging of the semi-dirty solvent obtained at the end of the cycleinto the tank for the semi-dirty solvent, continuing the intermittentintroduction of low-pressure air into the clean solvent which iscirculated; switching the valve so as to connect the line to the tankfor the semi-dirty solvent, interrupting the supply of low-pressure air;reversing the direction of rotation of the rotor of the pump so as tocause all the solvent contained in the lines to flow back into the tankfor the semi-dirty solvent; switching the valves and into theintercepting position; switching the valve so as to supply high-pressureair into the solvent conveying lines; and subsequent blowing of thehigh-pressure air through the valve so as to perform emptying andpartial drying of said lines using the high-pressure air; reconnectionto the tank containing the ink.
 14. Method according to claim 13, inwhich during the first washing step using semi-dirty solvent, the inkingcylinder is made to run at low speed, while during the subsequentwashing steps using semi-dirty solvent and clean solvent the inkingcylinder is made to run at high speed, alternating the rotation ineither direction so as to create a turbulence which removes the residualink from the chamber and from the cells of the cylinder.
 15. Method forautomatically washing the inking circuit in rotary printing pressesaccording to claim 14, characterized by the step of intermittentlyintroducing air into the flow of solvent circulated in the lines to bewashed, causing an intermittent acceleration of the body of solventinside the lines, which increases the action of separation of the inkfrom the walls of the lines by the solvent.
 16. Plant according to claim7, in which said pumps are pneumatic pumps of the double diaphragm type.17. Method for automatically washing the inking circuit in rotaryprinting presses according to claim 14, characterized by the step ofintermittently introducing air into the flow of solvent circulated inthe lines to be washed, causing an intermittent acceleration of the bodyof solvent inside the lines, which increases the action of separation ofthe ink from the walls of the lines by the solvent.